YSlow (with Firefox 3 support)

The plugin adds a new tab to Firebug console and do analyses on the page on opening. Though being criticized for some impractical rules like using content delivery network (CDN), it’s very useful tool for those who want to have general view of web app performance from client side. Following rules where you can (but don’t care much about grades it gives) you will see your web apps running faster while eating less bandwidth.

Image: YSlow in action

The team has released a new version of YSlow that works with Firefox 3. The new version includes:

clickable list of resources as a Table of Contents (“All CSS” and “All JS” features)

improved colors and presentation in the “legend” of component pies under Stats

fixed a bug where the same hostname with different port number was counted as a separate DNS lookup

misc bugfixes and style tweaks

This version supports all possible combinations of the different Firefox and Firebug development branches, namely the latest Firefox 2 and 3 and the latest Firebug releases: 1.05 (stable), 1.1 (beta) and 1.2 (beta).